Method and apparatus of small cell enhancement in a wireless communication system

ABSTRACT

A method and apparatus are disclosed to provide small cell enhancement in a wireless communication system. The method includes connecting to more than one serving cell. The method further includes triggering a Buffer Status Report (BSR) or a Power Headroom Report (PHR). The method further includes transmitting a Medium Access Control (MAC) control element corresponding to the BSR or the PHR in a serving cell, wherein the serving cell depends on a trigger of the BSR or the PHR.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present Application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/745,736 filed on Dec. 24, 2012, U.S. ProvisionalPatent Application Ser. No. 61/752,150 filed on Jan. 14, 2013, and U.S.Provisional Patent Application Ser. No. 61/768,761 filed on Feb. 25,2013, the entire disclosure of which are incorporated herein byreference.

FIELD

This disclosure generally relates to wireless communication networks,and more particularly, to methods and apparatuses for small cellenhancement in a wireless communication system.

BACKGROUND

With the rapid rise in demand for communication of large amounts of datato and from mobile communication devices, traditional mobile voicecommunication networks are evolving into networks that communicate withInternet Protocol (IP) data packets. Such IP data packet communicationcan provide users of mobile communication devices with voice over IP,multimedia, multicast and on-demand communication services.

An exemplary network structure for which standardization is currentlytaking place is an Evolved Universal Terrestrial Radio Access Network(E-UTRAN). The E-UTRAN system can provide high data throughput in orderto realize the above-noted voice over IP and multimedia services. TheE-UTRAN system's standardization work is currently being performed bythe 3GPP standards organization. Accordingly, changes to the currentbody of 3GPP standard are currently being submitted and considered toevolve and finalize the 3GPP standard.

SUMMARY

Methods and apparatuses are disclosed to provide small cell enhancementin a wireless communication system. One method includes connecting tomore than one serving cell. The method further includes triggering aBuffer Status Report (BSR) or a Power Headroom Report (PHR). The methodfurther includes transmitting a Medium Access Control (MAC) controlelement corresponding to the BSR or the PHR in a serving cell, whereinthe serving cell depends on a trigger of the BSR or the PHR.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a diagram of a wireless communication system according toone exemplary embodiment.

FIG. 2 is a block diagram of a transmitter system (also known as accessnetwork) and a receiver system (also known as user equipment or UE)according to one exemplary embodiment.

FIG. 3 is a functional block diagram of a communication system accordingto one exemplary embodiment.

FIG. 4 is a functional block diagram of the program code of FIG. 3according to one exemplary embodiment.

FIG. 5 is a diagram of deployment scenarios of small cell with and/orwithout macro coverage.

FIG. 6 is a diagram of UE buffer status forwarding between evolved NodeBs (eNBs).

FIG. 7 is a diagram of UE buffer status forwarding between evolved NodeBs (eNBs).

FIG. 8 is a flow diagram according to one exemplary embodiment.

FIG. 9 is a flow diagram according to one exemplary embodiment.

FIG. 10 is a flow diagram according to one exemplary embodiment.

FIG. 11 is a block diagram for a Medium Access Control (MAC) entity forControl Plane (C-plane).

FIG. 12 is a block diagram for a MAC entity for User Plane (U-plane).

FIG. 13 is a block diagram for a configuration of Inter-eNB CarrierAggregation.

FIG. 14 a flow diagram according to one exemplary embodiment.

DETAILED DESCRIPTION

The exemplary wireless communication systems and devices described belowemploy a wireless communication system, supporting a broadcast service.Wireless communication systems are widely deployed to provide varioustypes of communication such as voice, data, and so on. These systems maybe based on code division multiple access (CDMA), time division multipleaccess (TDMA), orthogonal frequency division multiple access (OFDMA),3GPP LTE (Long Term Evolution) wireless access, 3GPP LTE-A orLTE-Advanced (Long Term Evolution Advanced), 3GPP2 UMB (Ultra MobileBroadband), WiMax, or some other modulation techniques.

In particular, the exemplary wireless communication systems devicesdescribed below may be designed to support one or more standards such asthe standard offered by a consortium named “3rd Generation PartnershipProject” referred to herein as 3GPP, including Document Nos. RP-122033,“New Study Item Description: Small Cell enhancements for E-UTRA andE-UTRAN—Higher-layer aspects”, TR 36.932 V12.0.0, “Scenarios andRequirements of LTE Small Cell Enhancements”, TS 36.321 V11.0.0, “E-UTRAMAC protocol specification”, TS 36.331 V11.1.0, “E-UTRA RRC protocolspecification”, TS 36.300 V11.3.0, “E-UTRA and E-UTRAN Overalldescription; Stage 2”, TS 36.300 V11.4.0, “E-UTRA and E-UTRAN; Overalldescription; Stage 2”, TS 36.331 V11.2.0, “E-UTRA RRC protocolspecification (Release 11)”, RWS-120046, “Technologies for Rel-12 andonwards”, R2-130845, “TR 36.842 v0.1.0 on Study on Small CellEnhancements for E-UTRA and E-UTRAN—Higher-layer aspects”, NTT DOCOMO,TS 36.321 V11.1.0, “E-UTRA MAC protocol specification (Release 11)”. Thestandards, documents, and applications listed above are hereby expresslyincorporated by reference in their entirety.

FIG. 1 shows a multiple access wireless communication system accordingto one embodiment of the invention. An access network 100 (AN) includesmultiple antenna groups, one including 104 and 106, another including108 and 110, and an additional including 112 and 114. In FIG. 1, onlytwo antennas are shown for each antenna group, however, more or fewerantennas may be utilized for each antenna group. Access terminal 116(AT) is in communication with antennas 112 and 114, where antennas 112and 114 transmit information to access terminal 116 over forward link120 and receive information from access terminal 116 over reverse link118. Access terminal (AT) 122 is in communication with antennas 106 and108, where antennas 106 and 108 transmit information to access terminal(AT) 122 over forward link 126 and receive information from accessterminal (AT) 122 over reverse link 124. In a FDD system, communicationlinks 118, 120, 124 and 126 may use different frequency forcommunication. For example, forward link 120 may use a differentfrequency then that used by reverse link 118.

Each group of antennas and/or the area in which they are designed tocommunicate is often referred to as a sector of the access network. Inthe embodiment, antenna groups each are designed to communicate toaccess terminals in a sector of the areas covered by access network 100.

In communication over forward links 120 and 126, the transmittingantennas of access network 100 may utilize beamforming in order toimprove the signal-to-noise ratio of forward links for the differentaccess terminals 116 and 122. Also, an access network using beamformingto transmit to access terminals scattered randomly through its coveragecauses less interference to access terminals in neighboring cells thanan access network transmitting through a single antenna to all itsaccess terminals.

An access network (AN) may be a fixed station or base station used forcommunicating with the terminals and may also be referred to as anaccess point, a Node B, a base station, an enhanced base station, aneNB, or some other terminology. An access terminal (AT) may also becalled user equipment (UE), a wireless communication device, terminal,access terminal or some other terminology.

FIG. 2 is a simplified block diagram of an embodiment of a transmittersystem 210 (also known as the access network) and a receiver system 250(also known as access terminal (AT) or user equipment (UE)) in a MIMOsystem 200. At the transmitter system 210, traffic data for a number ofdata streams is provided from a data source 212 to a transmit (TX) dataprocessor 214.

In one embodiment, each data stream is transmitted over a respectivetransmit antenna. TX data processor 214 formats, codes, and interleavesthe traffic data for each data stream based on a particular codingscheme selected for that data stream to provide coded data.

The coded data for each data stream may be multiplexed with pilot datausing OFDM techniques. The pilot data is typically a known data patternthat is processed in a known manner and may be used at the receiversystem to estimate the channel response. The multiplexed pilot and codeddata for each data stream is then modulated (i.e., symbol mapped) basedon a particular modulation scheme (e.g., BPSK, QPSK, M-PSK, or M-QAM)selected for that data stream to provide modulation symbols. The datarate, coding, and modulation for each data stream may be determined byinstructions performed by processor 230.

The modulation symbols for all data streams are then provided to a TXMIMO processor 220, which may further process the modulation symbols(e.g., for OFDM). TX MIMO processor 220 then provides N_(T) modulationsymbol streams to N_(T) transmitters (TMTR) 222 a through 222 t. Incertain embodiments, TX MIMO processor 220 applies beamforming weightsto the symbols of the data streams and to the antenna from which thesymbol is being transmitted.

Each transmitter 222 receives and processes a respective symbol streamto provide one or more analog signals, and further conditions (e.g.,amplifies, filters, and upconverts) the analog signals to provide amodulated signal suitable for transmission over the MIMO channel. N_(T)modulated signals from transmitters 222 a through 222 t are thentransmitted from N_(T) antennas 224 a through 224 t, respectively.

At receiver system 250, the transmitted modulated signals are receivedby N_(R) antennas 252 a through 252 r and the received signal from eachantenna 252 is provided to a respective receiver (RCVR) 254 a through254 r. Each receiver 254 conditions (e.g., filters, amplifies, anddownconverts) a respective received signal, digitizes the conditionedsignal to provide samples, and further processes the samples to providea corresponding “received” symbol stream.

An RX data processor 260 then receives and processes the N_(R) receivedsymbol streams from N_(R) receivers 254 based on a particular receiverprocessing technique to provide N_(T) “detected” symbol streams. The RXdata processor 260 then demodulates, deinterleaves, and decodes eachdetected symbol stream to recover the traffic data for the data stream.The processing by RX data processor 260 is complementary to thatperformed by TX MIMO processor 220 and TX data processor 214 attransmitter system 210.

A processor 270 periodically determines which pre-coding matrix to use(discussed below). Processor 270 formulates a reverse link messagecomprising a matrix index portion and a rank value portion.

The reverse link message may comprise various types of informationregarding the communication link and/or the received data stream. Thereverse link message is then processed by a TX data processor 238, whichalso receives traffic data for a number of data streams from a datasource 236, modulated by a modulator 280, conditioned by transmitters254 a through 254 r, and transmitted back to transmitter system 210.

At transmitter system 210, the modulated signals from receiver system250 are received by antennas 224, conditioned by receivers 222,demodulated by a demodulator 240, and processed by a RX data processor242 to extract the reserve link message transmitted by the receiversystem 250. Processor 230 then determines which pre-coding matrix to usefor determining the beamforming weights then processes the extractedmessage.

Turning to FIG. 3, this figure shows an alternative simplifiedfunctional block diagram of a communication device according to oneembodiment of the invention. As shown in FIG. 3, the communicationdevice 300 in a wireless communication system can be utilized forrealizing the UEs (or ATs) 116 and 122 in FIG. 1, and the wirelesscommunications system is preferably the LTE system. The communicationdevice 300 may include an input device 302, an output device 304, acontrol circuit 306, a central processing unit (CPU) 308, a memory 310,a program code 312, and a transceiver 314. The control circuit 306executes the program code 312 in the memory 310 through the CPU 308,thereby controlling an operation of the communications device 300. Thecommunications device 300 can receive signals input by a user throughthe input device 302, such as a keyboard or keypad, and can outputimages and sounds through the output device 304, such as a monitor orspeakers. The transceiver 314 is used to receive and transmit wirelesssignals, delivering received signals to the control circuit 306, andoutputting signals generated by the control circuit 306 wirelessly.

FIG. 4 is a simplified block diagram of the program code 312 shown inFIG. 3 in accordance with one embodiment of the invention. In thisembodiment, the program code 312 includes an application layer 400, aLayer 3 portion 402, and a Layer 2 portion 404, and is coupled to aLayer 1 portion 406. The Layer 3 portion 402 generally performs radioresource control. The Layer 2 portion 404 generally performs linkcontrol. The Layer 1 portion 406 generally performs physicalconnections.

For LTE or LTE-A systems, the Layer 2 portion may include a Radio LinkControl (RLC) layer and a Medium Access Control (MAC) layer. The Layer 3portion may include a Radio Resource Control (RRC) layer.

3GPP RP-122033 approved a new study item entitled “New Study ItemDescription: Small Cell enhancements for E-UTRA and E-UTRAN—Higher-layeraspects” for LTE Rel-12. The justification and objective of the studyitem are quoted below:

-   -   3 Justification    -   Further enhancements for indoor and outdoor scenarios using        low-power nodes were identified as one of the most important        topics in the 3GPP workshop on Rel-12 and onward. According to        this big interest in small cell enhancements, scenarios and        requirements for small cell enhancements were studied and        captured in TR 36.932.    -   It is needed to study potential technologies of higher-layer        aspects for small cell enhancements taking into account these        scenarios and requirements (e.g., increased user throughput and        enhanced mobility performance).    -   4 Objective    -   The objective of this study is to identify potential        technologies in the protocol and architecture for enhanced        support of small cell deployment and operation which should        satisfy scenarios and requirements defined in TR 36.932.    -   The study shall be conducted on the following aspects:        -   Identify and evaluate the benefits of UEs having dual            connectivity to macro and small cell layers served by            different or same carrier and for which scenarios such dual            connectivity is feasible and beneficial.        -   Identify and evaluate potential architecture and protocol            enhancements for the scenarios in TR 36.932 and in            particular for the feasible scenario of dual connectivity            and minimize core network impacts if feasible, including:            -   Overall structure of control and user plane and their                relation to each other, e.g., supporting C-plane and                U-plane in different nodes, termination of different                protocol layers, etc.        -   Identify and evaluate the necessity of overall Radio            Resource Management structure and mobility enhancements for            small cell deployments:            -   Mobility mechanisms for minimizing inter-node UE context                transfer and signalling towards the core network.            -   Measurement and cell identification enhancements while                minimizing increased UE battery consumption.    -   For each potential enhancement, the gain, complexity and        specification impact should be assessed. The study shall focus        on potential enhancements which are not covered by other SI/WIs.

In 3GPP TR 36.932 V12.0.0, a small cell may be defined as follows:

-   -   Small cells using low power nodes are considered promising to        cope with mobile traffic explosion, especially for hotspot        deployments in indoor and outdoor scenarios. A low-power node        generally means a node whose Tx power is lower than macro node        and BS classes, for example Pico and Femto eNB are both        applicable.

Additionally, 3GPP TR 36.932 V12.0.0 mentions that the enhancements forsmall cells should target both with and without macro coverage, bothoutdoor and indoor small cell deployments, both ideal and non-idealbackhaul, and both sparse and dense small cell deployments. Anillustration of small cell deployment is shown in FIG. 5.

Furthermore, 3GPP TR 36.932 V12.0.0 also mentions the possiblecharacteristics of backhaul used by small cells as follows:

-   -   6.1.3 Ideal and non-ideal backhaul    -   Both ideal backhaul (i.e., very high throughput and very low        latency backhaul such as dedicated point-to-point connection        using optical fiber, LOS microwave) and non-ideal backhaul        (i.e., typical backhaul widely used in the market such as xDSL,        NLOS microwave, and other backhauls like relaying) should be        studied. The performance-cost trade-off should be taken into        account.    -   A categorization of non-ideal backhaul based on operator inputs        is listed in Table 6.1-1:

TABLE 6.1-1 Categorization of non-ideal backhaul Backhaul LatencyPriority Technology (One way) Throughput (1 is the highest) Fiber Access1 10-30 ms 10M-10 Gbps 1 Fiber Access 2  5-10 ms 100-1000 Mbps 2 DSLAccess 15-60 ms 10-100 Mbps 1 Cable 25-35 ms 10-100 Mbps 2 Wireless 5-35 ms 10 Mbps-100 Mbps 1 Backhaul typical, maybe up to Gbps rangeA categorization of good to ideal backhaul based on operator inputs islisted in Table 6.1-2:

TABLE 6.1-2 Categorization of good to ideal backhaul Backhaul LatencyPriority Technology (One way) Throughput (1 is the highest) Fiber 2-5 ms50M-10 Gbps 1

-   -   For interfaces between macro and small cell, as well as between        small cells, the studies should first identify which kind of        information is needed or beneficial to be exchanged between        nodes in order to get the desired improvements before the actual        type of interface is determined. And if direct interface should        be assumed between macro and small cell, as well as between        small cell and small cell, X2 interface can be used as a        starting point.

In one scenario, a macro cell and a small cell are controlled bydifferent eNBs 620 and 630. When a UE 610 has dual connectivity to themacro cell and the small cell at the same time, information exchangebetween the two eNBs 620 an 630 may be required. For example, in orderto realize C-plane and U-plane in different nodes (e.g., the macro cellfor C-plane and the small cell for U-plane), UE information received (asshown in step 640 of FIG. 6 and steps 720 and 730 of FIG. 7) by one eNB630 in FIGS. 6 and 620 in FIG. 7 (e.g., UE buffer status as shown instep 650 of FIG. 6 and step 740 of FIG. 7) may need to be delivered toanother proper eNB because there is currently no limitation about whichcell the UE information should be transmitted to. That is, the UEinformation can be transmitted to any serving cell in which an uplinkgrant is received as disclosed in 3GPP TS 36.321 V11.0.0. As a result,the latency of information exchange between the two eNBs, typically 2 to60 ms, is not negligible and would negatively impact the performance,such as increasing transmission delay. Moreover, the benefit ofoffloading the traffic of a macro cell may not be maximized because theradio resource of macro cell may be consumed to deliver information forsmall cell as shown in FIG. 7.

In various embodiments, methods are directed to eliminating orminimizing delay for information exchange between eNBs and offloadtraffic of macro cell to small cell. In these methods, C-plane andU-plane data are split as well as control information handled by MediumAccess Control (MAC) is split when a UE has dual connectivity to a macrocell and a small cell at the same time. The control informationincludes, but is not limited to, Buffer Status Report (BSR), PowerHeadroom Support (PHR), or Scheduling Request (SR).

In one embodiment, the BSR is divided into at least two categories. Byway of example and not of limitation, the categories of BSR are one istransmitted in macro cell(s), one is transmitted in small cell(s), oneis transmitted in serving cell(s) for C-plane, or one is transmitted inserving cell(s) for U-plane. For example, as shown in FIG. 8, at step810, a BSR is transmitted in one of serving cells which is a small cell630 (or is for U-plane) because the BSR transmission is triggered byU-plane data, e.g. from a Data Radio Bearer (DRB). The eNB controllingthe small cell 630 transmits an uplink grant to the UE 610 at step 820.At step 830, the U-plane data is transmitted to a serving cell, which isa small cell 630 (or is for U-plane). Additionally, FIG. 8 illustratesthat, at step 840, a BSR is transmitted in one of serving cells which isa macro cell 620 (or is for C-plane) because the BSR transmission istriggered by C-plane data. The eNB controlling a macro cell 620transmits an uplink grant to the UE 610 at step 850. At step 860, theC-plane data is transmitted to a serving cell, which is a macro cell620.

In one embodiment, a method of a UE includes: triggering a BSR andtransmitting a MAC control element corresponding to the BSR in aspecific serving cell, wherein the specific serving cell depends on atrigger of the BSR. At least one of the following transmission rules ofthe MAC control element could be used:

-   -   If the trigger is higher priority data arrival from a specific        logical channel (or logical channel group (as disclosed in 3GPP        TS 36.331 V11.1.0) or Radio Bearer (RB) (as disclosed in 3GPP TS        36.331 V11.1.0)), the MAC control element should be transmitted        in a serving cell (of a serving cell group) corresponding to the        logical channel (or logical channel group or RB).    -   If the trigger is higher priority data arrival from U-plane,        e.g. a DRB, the MAC control element should be transmitted in a        serving cell which is configured to receive U-plane data.    -   If the trigger is a periodic buffer status reporting timer        expiry, the MAC control element should be transmitted in a        serving cell (of a serving cell group) corresponding to the        periodic buffer status reporting timer.    -   If the trigger is a buffer status retransmission timer expiry,        the MAC control element should be transmitted in a serving cell        (of a serving cell group) corresponding to the buffer status        retransmission timer.    -   If the trigger is higher priority data arrival from a specific        logical channel (or logical channel group or RB), the MAC        control element should be transmitted by a MAC entity        corresponding to the logical channel (or logical channel group        or RB).    -   If the trigger is higher priority data arrival from U-plane,        e.g. a DRB, the MAC control element should be transmitted by a        MAC entity which is used to transmit U-plane data.    -   If the trigger is a periodic buffer status reporting timer        expiry, the MAC control element should be transmitted by a MAC        entity corresponding to the periodic buffer status reporting        timer.    -   If the trigger is a buffer status retransmission timer expiry,        the MAC control element should be transmitted by a MAC entity        corresponding to the buffer status retransmission timer.

In the above embodiment, more than one periodic buffer status reportingtimer, e.g. periodicBSR-Timer as disclosed in 3GPP TS 36.321 V11.0.0, isused to trigger a BSR. More than one buffer status retransmission timer,e.g. retxBSR-Timer as disclosed in 3GPP TS 36.321 V11.0.0, is used totrigger a BSR. The MAC control element does not include status ofbuffered data which can't be transmitted in the serving cell. In otherwords, the MAC control element only includes status of buffered datawhich can be transmitted in the serving cell.

In one embodiment, the PHR is divided into at least two categories. Byway of example and not of limitation, the categories of the PHR are onetransmitted in macro cell(s), one transmitted in small cell(s), one istransmitted in serving cell(s) for C-plane, or one transmitted inserving cell(s) for U-plane. For example, as shown in FIG. 9, at step940, a PHR is transmitted in one of serving cells which is a small cell630 (or is for U-plane) because the PHR transmission is triggered by asmall cell 630 (or a serving cell for U-plane), e.g., due to path losschange. At step 930, the eNB controlling the small cell 630 transmits anuplink grant to the UE 610. Additionally, FIG. 9 illustrates that, atstep 920, a PHR is transmitted in one of serving cells which is a macrocell 620 (or is for C-plane) because the PHR transmission is triggeredby a macro cell 620 (or a serving cell for C-plane), e.g., due to pathloss change. The eNB controlling a macro cell 620 transmits an uplinkgrant to the UE 610 at step 910.

In one embodiment, a method of a UE includes: triggering a PHR andtransmitting a MAC control element corresponding to the PHR in aspecific serving cell, wherein the specific serving cell depends on atrigger of the PHR. At least one of the following transmission rules ofthe MAC control element could be used:

-   -   If the trigger is path loss change for a first serving cell, the        MAC control element should be transmitted in a second serving        cell of a serving cell group including the first serving cell.        The first serving cell and the second serving cell can be the        same serving cell.    -   If the trigger is a periodic power headroom reporting timer        expiry, the MAC control element should be transmitted in a        serving cell of a serving cell group corresponding to the        periodic power headroom reporting timer.    -   If the trigger is path loss change for a serving cell, the MAC        control element should be transmitted by a MAC entity        corresponding to the serving cell.    -   If the trigger is a periodic power headroom reporting timer        expiry, the MAC control element should be transmitted by a MAC        entity corresponding to the periodic power headroom reporting        timer.

In the above embodiment, more than one periodic power headroom reportingtimer, e.g. periodicPHR-Timer as disclosed in 3GPP TS 36.321 V11.0.0, isused to trigger a PHR. The MAC control element transmitted in a thirdserving cell does not include status of power headroom for a fourthserving cell if the third serving cell and the fourth serving cell arenot included in the same serving cell group. In other words, the MACcontrol element transmitted in the third serving cell only includesstatus of power headroom for serving cell(s) that belongs to the samegroup as the third serving cell.

In one embodiment, a SR is divided into at least two categories. By wayof example and not of limitation, the categories of the SR are onetransmitted in macro cell(s), one transmitted in small cell(s), onetransmitted in serving cell(s) for C-plane, or one transmitted inserving cell(s) for U-plane. For example, as shown in FIG. 10, at step1010, a SR is transmitted on a Physical Uplink Control Channel (PUCCH)resource for SR in one of serving cells which is a small cell 630 (or isfor U-plane) because the SR is triggered by a BSR transmission which istriggered by U-plane data (e.g., from a DRB). At step 1020, the eNBcontrolling the small cell 630 transmits an uplink grant to the UE 610.Additionally, FIG. 10 illustrates that, at step 1030, a SR istransmitted on a PUCCH resource for SR in one of serving cells which isa macro cell 620 (or is for C-plane) because the SR is triggered by aBSR transmission which is triggered by C-plane data (e.g., from a DRB).At step 1040, the eNB controlling the macro cell 620 transmits an uplinkgrant to the UE 610.

In one embodiment, a method of a UE includes: triggering a BSR. Themethod further includes triggering a SR due to the BSR and transmittingthe SR on PUCCH of a specific serving cell, wherein the specific servingcell depends on a trigger of the BSR. At least one of the followingtransmission rules of the SR could be used:

-   -   If the trigger is higher priority data arrival from a specific        logical channel (or logical channel group or RB), the SR should        be transmitted on PUCCH of a serving cell (of a serving cell        group) corresponding to the logical channel (or logical channel        group or RB).    -   If the trigger is higher priority data arrival from U-plane,        e.g. a DRB, the SR should be transmitted on PUCCH of a serving        cell which is configured to receive U-plane data.    -   If the trigger is higher priority data arrival from a specific        logical channel (or logical channel group or RB), the SR should        be transmitted by a MAC entity corresponding to the logical        channel (or logical channel group or RB).    -   If the trigger is higher priority data arrival from U-plane,        e.g. a DRB, the SR should be transmitted by a MAC entity which        is used to transmit U-plane data.

In the above embodiment, the SR is transmitted on a PUCCH of a servingcell corresponding to the MAC entity. PUCCH resource for SR isconfigured in more than one serving cell of the UE, e.g. in one cell forC-plane data and in the other one cell for U-plane data, or in one cellfor a MAC entity and in the other cell for another MAC entity, or in onecell which is a small cell and in the other cell which is a macro cell,or in cells controlled by different eNBs.

In these embodiments, mapping between the timer and the serving cell (ora group of serving cells including the serving cell) is configured.Mapping between the timer and the MAC entity is configured. The MACcontrol element is transmitted in a serving cell corresponding to theMAC entity. Mapping between the logical channel (or logical channelgroup or RB) and the serving cell (or a group of serving cells includingthe serving cell) is configured. Mapping between the logical channel (orlogical channel group or RB) and the MAC entity is configured. Mappingbetween the MAC entity and the serving cell (or a group of servingcells) is configured. The mapping may be configured according toinformation provided by network. More than one MAC entity is used by theUE, e.g. one for C-plane data and the other one for U-plane data, or onefor small cells and the other one for macro cells, or one MAC entitycorresponds to one eNB. Serving cells of the UE are divided into morethan one group, e.g. one group for C-plane data and the other group forU-plane data, or one group for a MAC entity and the other group foranother MAC entity, or one group is small cells and the other group ismacro cells, or serving cells controlled by the same eNB are in the samegroup. C-plane data includes data from Signaling Radio Bearer (SRB) (asdisclosed in 3GPP TS 36.331 V11.1.0). U-plane data includes data fromDRB (as disclosed in 3GPP TS 36.331 V11.1.0).

In another embodiment, a UE has more than one Medium Access Control(MAC) entity. For example, the UE may have a MAC entity for C-plane, onefor U-plane, one for macro cell(s) or one for small cell(s). Each MACentity has its own Discontinuous Reception (DRX) operation (e.g. when tomonitor PDCCH), measurement gap configuration as defined in 3GPP TS36.331 V11.1.0, BSR procedure (for triggering or transmitting), PHRprocedure (for triggering or transmitting), and/or SR procedure (fortriggering or transmitting with its own SR resource). According to oneembodiment, the determination of how to apply a received MAC controlelement depends on where it received. For example, a DRX command MACcontrol element is applied to a DRX procedure of a MAC entity whichreceives the DRX command MAC control element.

FIG. 11 illustrates one embodiment of a relation 1100 between MAC entityfor C-plane 1120, an upper layer 1110 of the MAC entity for C-plane1120, and a lower layer 1130 of the MAC entity for C-plane 1120. Asshown in FIG. 11, the upper layer 1110 includes PCCH 1111, MCCH 1112,MTCH 1113, BCCH 1114, CCCH 1115, DCCH 1116, and a MAC control 117. TheMAC entity for C-plane 1120 includes a Control 1121 in communicationwith Logical Channel Prioritization (UL only) 1122, (De-) Multiplexing1123, De Multiplexing 1124, HARQ 1125, and Random Access Control 1126.The lower layer 1130 includes PCH 1131, MCH 1132, BCH 1133, DL-SCH 1134,UL-SCH 1135, and RACH 1136.

FIG. 12 illustrates one embodiment of a relation 1200 between MAC entityfor U-plane 1220, an upper layer 1210 of the MAC entity for U-plane1220, and a lower layer 1230 of the MAC entity for U-plane 1220. Asshown in FIG. 12, the upper layer 1210 includes DTCH 1212 and MACcontrol 1214. The MAC entity for U-plane 1220 includes a Control 1221 incommunication with Logical Channel Prioritization (UL only) 1222, (De-)Multiplexing 1223, HARQ 1224, and Random Access Control 1225. The lowerlayer 1230 includes DL-SCH 1232, UL-SCH 1234, and RACH 1236.

Besides, in this scenario with dual connectivity to macro and smallcells, there is an issue of whether C-plane and U-plane need to beseparated completely based upon the cell type. For example, the macrocell may be assigned for C-plane data, and the small cell is assignedfor U-plane data. It is assumed that C-plane and U-plane assigned todifferent nodes in order to ease the loading of the macro cell by movingU-plane loading to small cells. However, the macro cell may havesufficient radio resources to handle U-plane data in a situation wherethe traffic loading is low. Accordingly, the restriction of completelyseparating C-plane and U-plane would not be necessary.

Various embodiments are directed to network control of the separation ofC-plane and U-plane in order to enhance performance of the cells andflexibly distribute the loading for C-plane and U-plane among the cells.In one embodiment, the separation depends on the loading of the cells.In another embodiment, separation is based on a RB basis. In anotherembodiment, separation is based upon a logical channel basis. In yetanother embodiment, separation is based upon a logical channel groupbasis.

In one embodiment, mapping between a RB (or a logical channel or alogical channel group) and a serving cell (or a group of serving cells,an eNB, or a MAC entity) is configured according to information providedby the eNB.

In one embodiment, a method of a UE includes: receiving a signaling toconfigure a mapping corresponding to a data category; and transmitting adata of the data category based on the mapping.

In another embodiment, a method of an eNB includes: transmitting asignaling to configure a mapping corresponding to a data category, inwhich the mapping is used to inform a UE to transmit a data of the datacategory based on the mapping.

Additionally, transmitting the data based on the mapping means thatwhere, how, or which radio resources are to be used to transmit the datais according to the mapping, e.g., the data is allowed to be transmittedin a specific cell.

In one embodiment, a method of a UE includes: receiving a signaling toconfigure a mapping corresponding to a data category; and receiving adata of the data category based on the mapping.

In another embodiment, a method of an eNB includes: transmitting asignaling to configure a mapping corresponding to a data category, inwhich the mapping is used to inform a UE to receive a data of the datacategory based on the mapping.

Additionally, receiving the data based on the mapping means that where,how, or which radio resources are to be used to receive the data isaccording to the mapping, e.g., receiving the data in a specific cell.

In these embodiments, the signaling can be a RRC connectionreconfiguration message. Alternatively, the signaling can be a messageused to configure Carrier Aggregation.

In these embodiments, the mapping further includes at least one of thefollowing relationships

-   -   A relationship between the data category and a serving cell.    -   A relationship between the data category and a group of serving        cells. The small cells belong to the same group, the macro cells        belong to the same group, or cells controlled by the same eNB        belong to the same group.    -   A relationship between the data category and an eNB.    -   A relationship between the data category and a MAC entity.

In these embodiments, the data category can be categorized based on aRB, logical channel, or logical channel group. Accordingly, data for thesame RB belongs to the same data category. Alternatively, data for thesame logical channel belongs to the same data category, or data for thesame logical channel group belongs to the same data category.Alternatively, the data category can be categorized based on a type ofdata plane. For example, U-plane data is one data category and C-planedata is another data category.

In these embodiments, the signaling indicates information correspondingto a size of a cell, e.g. a weight for a cell. The signaling may alsoindicate information corresponding to a type of a cell, e.g. macro orsmall. Additionally, the signaling may indicate a mapping betweencell(s) and eNB(s) or a mapping between MAC entities and cells.

Additionally, to achieve dual connectivity of macro and small cells,carrier aggregation (CA) is a feasible mechanism. Currently the stage-2and stage-3 description of CA are specified in 3GPP TS 36.300 V11.4.0and TS 36.331 V11.2.0, respectively. While the currently specified CA isused for intra-eNB, inter-eNB CA, where the macro and the small cellsare controlled by different eNBs, has also been considered (see e.g.,RWS-120046) to achieve dual connectivity in small cell enhancement. Asdisclosed in RWS-120046, a possible architecture of inter-eNB CA 1300 isshown in FIG. 13. As shown in FIG. 13, a network node 1310 called“Serving eNB” controls a macro cell and a network node 1320 called“Drift eNB” controls a small cell.

While 3GPP TR 36.932 v12.0.0 and R2-130845 focus on the deploymentscenarios of macro and pico cells connected via non-ideal backhaul,fibre access, which can be used to deploy Remote Radio Heads (RRHs), isnot assumed in this study item.

Dual connectivity is considered as one potential enhancement for smallcells. Under the scenario of dual connectivity, C-plane and U-plane indifferent nodes, e.g. eNBs, may be supported.

In order to transmit data, such as C-plane and U-plane data, the networkneeds to be informed about buffer status to acquire respective uplinkresources in different cells. To achieve C-plane and U-plane separation,separation based on per logical channel (group) basis is a possibility.That is, data from some logical channels (e.g., corresponding to SRB(s))is transmitted in some cell(s) (e.g., macro cells), and data from otherlogical channels, (e.g., corresponding to DRB(s)) is transmitted inother cell(s) (e.g., pico cells). As a consequence, different networknodes should be informed about the UE buffer status to schedule properuplink resource to the UE.

According to the current Buffer Status Reporting as disclosed in 3GPP TS36.321 V11.1.0, the UE could transmit buffer status in any serving cell.However, since the current scenario has macro cells and pico cellsconnected via non-ideal backhaul, transferring received UE buffer statusbetween macro cells and pico cells may result in unacceptable schedulingdelay and poor uplink performance. In order to avoid delay and poorperformance, both macro cells and pico cells can be informed about UEbuffer status directly by the UE. However, whether the informationprovided by a Buffer Status Report (BSR) is feasible to the deploymentscenarios with small cells is not fully addressed. If a BSR cannotprovide proper information, scheduling delay and poor uplink performancemay still result. BSR as discussed in 3GPP TS 36.321 V11.1.0 is quotedbelow:

-   -   5.4.5 Buffer Status Reporting    -   The Buffer Status reporting procedure is used to provide the        serving eNB with information about the amount of data available        for transmission in the UL buffers of the UE. RRC controls BSR        reporting by configuring the two timers periodicBSR-Timer and        retxBSR-Timer and by, for each logical channel, optionally        signalling logicalChannelGroup which allocates the logical        channel to an LCG [8].    -   For the Buffer Status reporting procedure, the UE shall consider        all radio bearers which are not suspended and may consider radio        bearers which are suspended.    -   A Buffer Status Report (BSR) shall be triggered if any of the        following events occur:        -   UL data, for a logical channel which belongs to a LCG,            becomes available for transmission in the RLC entity or in            the PDCP entity (the definition of what data shall be            considered as available for transmission is specified in [3]            and [4] respectively) and either the data belongs to a            logical channel with higher priority than the priorities of            the logical channels which belong to any LCG and for which            data is already available for transmission, or there is no            data available for transmission for any of the logical            channels which belong to a LCG, in which case the BSR is            referred below to as “Regular BSR”;        -   UL resources are allocated and number of padding bits is            equal to or larger than the size of the Buffer Status Report            MAC control element plus its subheader, in which case the            BSR is referred below to as “Padding BSR”;        -   retxBSR-Timer expires and the UE has data available for            transmission for any of the logical channels which belong to            a LCG, in which case the BSR is referred below to as            “Regular BSR”;        -   periodicBSR-Timer expires, in which case the BSR is referred            below to as “Periodic BSR”.    -   For Regular and Periodic BSR:        -   if more than one LCG has data available for transmission in            the TTI where the BSR is transmitted: report Long BSR;        -   else report Short BSR.    -   For Padding BSR:        -   if the number of padding bits is equal to or larger than the            size of the Short BSR plus its subheader but smaller than            the size of the Long BSR plus its subheader:            -   if more than one LCG has data available for transmission                in the TTI where the BSR is transmitted: report                Truncated BSR of the LCG with the highest priority                logical channel with data available for transmission;            -   else report Short BSR.        -   else if the number of padding bits is equal to or larger            than the size of the Long BSR plus its subheader, report            Long BSR.    -   If the Buffer Status reporting procedure determines that at        least one BSR has been triggered and not cancelled:        -   if the UE has UL resources allocated for new transmission            for this TTI:            -   instruct the Multiplexing and Assembly procedure to                generate the BSR MAC control element(s);            -   start or restart periodicBSR-Timer except when all the                generated BSRs are Truncated BSRs;            -   start or restart retxBSR-Timer.        -   else if a Regular BSR has been triggered:            -   if an uplink grant is not configured or the Regular BSR                was not triggered due to data becoming available for                transmission for a logical channel for which logical                channel SR masking (logicalChannelSR-Mask) is setup by                upper layers:                -   a Scheduling Request shall be triggered.    -   A MAC PDU shall contain at most one MAC BSR control element,        even when multiple events trigger a BSR by the time a BSR can be        transmitted in which case the Regular BSR and the Periodic BSR        shall have precedence over the padding BSR.    -   The UE shall restart retxBSR-Timer upon indication of a grant        for transmission of new data on any UL-SCH.    -   All triggered BSRs shall be cancelled in case the UL grant(s) in        this subframe can accommodate all pending data available for        transmission but is not sufficient to additionally accommodate        the BSR MAC control element plus its subheader. All triggered        BSRs shall be cancelled when a BSR is included in a MAC PDU for        transmission.    -   The UE shall transmit at most one Regular/Periodic BSR in a TTI.        If the UE is requested to transmit multiple MAC PDUs in a TTI,        it may include a padding BSR in any of the MAC PDUs which do not        contain a Regular/Periodic BSR.    -   All BSRs transmitted in a TTI always reflect the buffer status        after all MAC PDUs have been built for this TTI. Each LCG shall        report at the most one buffer status value per TTI and this        value shall be reported in all BSRs reporting buffer status for        this LCG.    -   NOTE: A Padding BSR is not allowed to cancel a triggered        Regular/Periodic BSR. A Padding BSR is triggered for a specific        MAC PDU only and the trigger is cancelled when this MAC PDU has        been built.

According to Buffer Status Reporting as quoted above, a Truncated BSRMAC control element reports buffer status of a logical channel groupwith the highest priority logical channel with data available fortransmission. That is, the truncated BSR MAC control element reports themost important buffer status. However, a logical channel group with thehighest priority logical channel with data available for transmissionmay not be handled by the network node that received the Truncated BSRMAC control element. Accordingly, the network may not be able to receivenecessary UE buffer status or transferring UE buffer status may still berequired. Thus, there is a need to minimize the risk of scheduling delayand poor uplink performance.

In various embodiments disclosed herein, when a UE decides the contentof a Truncated BSR MAC control element, the UE should make the decisionbased not only on the priority of logical channels with data availablefor transmission but also taking into account the mapping betweenlogical channels and serving cells. Alternatively, the UE should alsomake the decision by taking into account the serving cell the TruncatedBSR MAC control element will be transmitted in. However, the trade-offis the network may lose the chance to acquire the most important bufferstatus, i.e., the buffer status of a logical channel group with thehighest priority logical channel with data available for transmission.

Generally, in one embodiment, when receiving an uplink resource totransmit a Truncated BSR MAC control element in a specific serving cell,the UE should indicate buffer status corresponding to a specific logicalchannel group by the Truncated BSR MAC control element. The specificlogical channel group includes a logical channel having highest priorityamong a set of established logical channels mapping to the specificserving cell and with data available for transmission, but the specificlogical channel may not have the highest priority among all establishedlogical channels with data available for transmission.

In one embodiment, a logical channel mapping to a serving cell meansthat data from the logical channel is allowed to be transmitted in theserving cell. The UE may have dual connectivity to macro and small celllayers. C-plane and U-plane of the UE could be handled by differentnetwork nodes. The UE may be configured Carrier Aggregation with servingcells controlled by different eNBs. When deciding the content of a LongBSR MAC control element (transmitted in a macro cell or a pico cell),the criteria mentioned above, e.g. mapping or cell to transmit the BSRMAC control element, may not need to be taken into account.

FIG. 14 illustrates one method of a UE. At step 1410, the method isstarted. At step 1420, a condition to provide a Truncated BSR MACcontrol element is fulfilled. At step 1430, a determination is maderegarding the content of the Truncated BSR MAC control element based onconditions, including, but not limited to, the mapping between logicalchannels and serving cells. At step 1440, return.

In one embodiment, a method of a UE utilizing at least two serving cellsis disclosed. In this method, the UE connects to at least two servingcells, including a first serving cell and a second serving cell. Atleast two logical channels are established, including a first logicalchannel which belongs to a first logical channel group and a secondlogical channel which belongs to a second logical channel group. In oneembodiment, the first logical channel has higher priority than thesecond logical channel. The first logical channel is mapped to at leastthe first serving cell but not to the second serving cell. The secondlogical channel is mapped to at least the second serving cell. An uplinkgrant is received for a transmission in the second serving cell. Adetermination is made and confirmed that a condition to include a BSRMAC control element in the transmission is fulfilled and both the firstlogical channel and the second logical channel have data available fortransmission. The BSR MAC control element indicates buffer statuscorresponding to the second logical channel group when the secondlogical channel has highest priority among a set of established logicalchannels mapping to at least the second serving cell and with dataavailable for transmission.

In one embodiment, the first serving cell is Primary Cell (PCell) or amacro cell. In one embodiment, the second serving cell is a SecondaryCell (SCell) or a pico cell. In one embodiment, the first serving celland the second serving cell are controlled by different eNBs.

In one embodiment, the first logical channel corresponds to a SRB.Additionally, in one embodiment, the first logical channel has highestpriority among all established logical channels. In another embodiment,the first logical channel group does not include a logical channelmapping the second serving cell.

In one embodiment, the second logical channel corresponds to a DRB.Additionally, in one embodiment, the second logical channel is notmapping to the first serving cell. In another embodiment, the secondlogical channel group does not include a logical channel mapping thefirst serving cell.

In one embodiment, data from the first logical channel and data from thesecond logical channel are transmitted by different MAC entities.Alternatively, data from the first logical channel and data from thesecond logical channel are transmitted by the same MAC entity. Inanother embodiment, the mapping between logical channels and servingcells are configured by network. In one embodiment, a logical channelmapping to a serving cell means that data from the logical channel isallowed to be transmitted in the serving cell. In another embodiment,data from a logical channel cannot be transmitted to a serving cell thatis not mapped to the logical channel.

In one embodiment, the BSR MAC control element includes buffer statuscorresponding to only one logical channel group. In another embodiment,the BSR MAC control element is a Truncated BSR MAC control element. Inanother embodiment, the BSR MAC control element is generated due to aPadding BSR.

In one embodiment, the set of established logical channels consists ofall established logical channels mapping to at least the second servingcell and with data available for transmission.

In one embodiment, the condition to include the BSR MAC control elementin a MAC PDU is the number of padding bits in the MAC PDU that is equalto or larger than the size of a Short BSR MAC control element plus itssubheader but smaller than the size of a Long BSR MAC control elementplus its subheader if more than one logical channel group has dataavailable for transmission in the TTI where a BSR MAC control element istransmitted.

In one embodiment, when receiving another uplink grant for anothertransmission in the first serving cell and a condition to include a LongBSR MAC control element in the another transmission is fulfilled andboth the first logical channel and the second logical channel have dataavailable for transmission, indicating, in the Long BSR MAC controlelement, both buffer status corresponding to the first logical channelgroup and buffer status corresponding to the second logical channelgroup.

In one embodiment, when receiving another uplink grant for anothertransmission in the second serving cell and a condition to include aLong BSR MAC control element in the another transmission is fulfilledand both the first logical channel and the second logical channel havedata available for transmission, indicating, in the Long BSR MAC controlelement, both buffer status corresponding to the first logical channelgroup and buffer status corresponding to the second logical channelgroup.

In one embodiment, when receiving another uplink grant for anothertransmission in the second serving cell and a condition to include aLong BSR MAC control element in the another transmission is fulfilledand both the first logical channel and the second logical channel havedata available for transmission, indicating, in the Long BSR MAC controlelement, buffer status corresponding to the second logical channel groupbut not buffer status corresponding to the first logical channel group.

In one embodiment, when receiving another uplink grant for anothertransmission in the second serving cell and a condition to include theBSR MAC control element in the another transmission is fulfilled and thefirst logical channel has data available for transmission and the secondlogical channel does not have data available for transmission,indicating, in the BSR MAC control element, buffer status correspondingto the first logical channel group when the set of established logicalchannels is empty and the first logical channel has highest priorityamong all established logical channels with data available fortransmission.

Referring back to FIGS. 3 and 4, the device 300 includes a program code312 stored in memory 310. In one embodiment, the CPU 308 could executeprogram code 312 to execute one or more of the following: (i) to connectto more than one serving cell, (ii) to trigger a Buffer Status Report(BSR) or a Power Headroom Report (PHR), and (iii) to transmit a MediumAccess Control (MAC) control element corresponding to the BSR or the PHRin a serving cell, wherein the serving cell depends on a trigger of theBSR or the PHR.

In another embodiment, the CPU 308 could execute the program code 312 toexecute one or more of the following: (i) to connect to more than oneserving cell, (ii) to receive a signaling to configure a mappingcorresponding to a data category, and (iii) to transmit or receive adata of the data category in a serving cell, wherein the serving cell isbased on the mapping.

In yet another embodiment, the CPU 308 could execute the program code312 to execute one or more of the following: (i) to connect to at leasttwo serving cells, including a first serving cell and a second servingcell, (ii) to establish at least two logical channels, including a firstlogical channel and a second logical channel, wherein the first logicalchannel belongs to a first logical channel group and is mapping to atleast the first serving cell but not to the second serving cell, and thesecond logical channel belongs to a second logical channel group and ismapping to at least the second serving cell, and wherein the firstlogical channel has higher priority than the second logical channel,(iii) to receive an uplink grant for a transmission in the secondserving cell, (iv) to include a Buffer Status Report (BSR) Medium AccessControl (MAC) control element in the transmission, wherein both thefirst logical channel and the second logical channel have data availablefor transmission, and (v) to indicate, in the BSR MAC control element, abuffer status corresponding to the second logical channel group when thesecond logical channel has the highest priority among a set ofestablished logical channels mapping to at least the second serving celland with data available for transmission, wherein the BSR MAC controlelement includes buffer status corresponding to only one logical channelgroup.

In addition, the CPU 308 can execute the program code 312 to perform allof the above-described actions and steps or others described herein.

Various aspects of the disclosure have been described above. It shouldbe apparent that the teachings herein may be embodied in a wide varietyof forms and that any specific structure, function, or both beingdisclosed herein is merely representative. Based on the teachings hereinone skilled in the art should appreciate that an aspect disclosed hereinmay be implemented independently of any other aspects and that two ormore of these aspects may be combined in various ways. For example, anapparatus may be implemented or a method may be practiced using anynumber of the aspects set forth herein. In addition, such an apparatusmay be implemented or such a method may be practiced using otherstructure, functionality, or structure and functionality in addition toor other than one or more of the aspects set forth herein. As an exampleof some of the above concepts, in some aspects concurrent channels maybe established based on pulse repetition frequencies. In some aspectsconcurrent channels may be established based on pulse position oroffsets. In some aspects concurrent channels may be established based ontime hopping sequences. In some aspects concurrent channels may beestablished based on pulse repetition frequencies, pulse positions oroffsets, and time hopping sequences.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, processors, means, circuits, and algorithmsteps described in connection with the aspects disclosed herein may beimplemented as electronic hardware (e.g., a digital implementation, ananalog implementation, or a combination of the two, which may bedesigned using source coding or some other technique), various forms ofprogram or design code incorporating instructions (which may be referredto herein, for convenience, as “software” or a “software module”), orcombinations of both. To clearly illustrate this interchangeability ofhardware and software, various illustrative components, blocks, modules,circuits, and steps have been described above generally in terms oftheir functionality. Whether such functionality is implemented ashardware or software depends upon the particular application and designconstraints imposed on the overall system. Skilled artisans mayimplement the described functionality in varying ways for eachparticular application, but such implementation decisions should not beinterpreted as causing a departure from the scope of the presentdisclosure.

In addition, the various illustrative logical blocks, modules, andcircuits described in connection with the aspects disclosed herein maybe implemented within or performed by an integrated circuit (“IC”), anaccess terminal, or an access point. The IC may comprise a generalpurpose processor, a digital signal processor (DSP), an applicationspecific integrated circuit (ASIC), a field programmable gate array(FPGA) or other programmable logic device, discrete gate or transistorlogic, discrete hardware components, electrical components, opticalcomponents, mechanical components, or any combination thereof designedto perform the functions described herein, and may execute codes orinstructions that reside within the IC, outside of the IC, or both. Ageneral purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

It is understood that any specific order or hierarchy of steps in anydisclosed process is an example of a sample approach. Based upon designpreferences, it is understood that the specific order or hierarchy ofsteps in the processes may be rearranged while remaining within thescope of the present disclosure. The accompanying method claims presentelements of the various steps in a sample order, and are not meant to belimited to the specific order or hierarchy presented.

The steps of a method or algorithm described in connection with theaspects disclosed herein may be embodied directly in hardware, in asoftware module executed by a processor, or in a combination of the two.A software module (e.g., including executable instructions and relateddata) and other data may reside in a data memory such as RAM memory,flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a harddisk, a removable disk, a CD-ROM, or any other form of computer-readablestorage medium known in the art. A sample storage medium may be coupledto a machine such as, for example, a computer/processor (which may bereferred to herein, for convenience, as a “processor”) such theprocessor can read information (e.g., code) from and write informationto the storage medium. A sample storage medium may be integral to theprocessor. The processor and the storage medium may reside in an ASIC.The ASIC may reside in user equipment. In the alternative, the processorand the storage medium may reside as discrete components in userequipment. Moreover, in some aspects any suitable computer-programproduct may comprise a computer-readable medium comprising codesrelating to one or more of the aspects of the disclosure. In someaspects a computer program product may comprise packaging materials.

While the invention has been described in connection with variousaspects, it will be understood that the invention is capable of furthermodifications. This application is intended to cover any variations,uses or adaptation of the invention following, in general, theprinciples of the invention, and including such departures from thepresent disclosure as come within the known and customary practicewithin the art to which the invention pertains.

The invention claimed is:
 1. A method of a User Equipment (UE), themethod comprising: connecting to multiple serving cells; triggering aBuffer Status Report (BSR) due to expiry of a periodic buffer statusreporting timer; triggering a Scheduling Request (SR) due to thetriggering of the BSR; transmitting the SR on a Physical Uplink ControlChannel (PUCCH) of a second serving cell, and transmitting a MediumAccess Control (MAC) control element corresponding to the BSR in a firstserving cell; wherein the first serving cell is selected based on wherean uplink grant is received if the connected serving cells arecontrolled by a same evolved Node B (eNB), and wherein multiple periodicbuffer status reporting timers are used to trigger the BSR and the firstserving cell corresponds to the expired periodic buffer status reportingtimer if the connected serving cells are controlled by different eNBs,and wherein a mapping between the multiple periodic buffer statusreporting timers and the connected serving cells is configured accordingto information provided by network, and each of the multiple periodicbuffer status reporting timers corresponds to one or a group of theconnected serving cells, and wherein the MAC control element includesstatus of buffered data which can be transmitted in the first servingcell and does not include status of buffered data which cannot betransmitted in the first serving cell, and wherein the second servingcell is selected based on the trigger of the BSR, and a PUCCH resourcefor the SR is configured in more than one of the connected serving cellsof the UE.
 2. The method of claim 1, wherein a mapping between MACentities and the connected serving cells is configured according to theinformation provided by the network.
 3. The method of claim 1, whereinmultiple MAC entities are used by the UE when the connected servingcells are controlled by the different eNBs and one MAC entitycorresponds to one eNB.
 4. A communication device for implementing smallcell enhancement, comprising: a control circuit; a processor installedin the control circuit; a memory installed in the control circuit andoperatively coupled to the processor; wherein the processor isconfigured to execute a program code stored in the memory to implementsmall cell enhancement by: connecting to at least two serving cells,including a first serving cell and a second serving cell; establishingat least two logical channels, including a first logical channel and asecond logical channel, wherein the first logical channel belongs to afirst logical channel group and is mapping to at least the first servingcell but not to the second serving cell, and the second logical channelbelongs to a second logical channel group and is mapping to at least thesecond serving cell, and wherein the first logical channel has higherpriority than the second logical channel; receiving an uplink grant fora transmission in the second serving cell; including a Buffer StatusReport (BSR) Medium Access Control (MAC) control element in thetransmission, wherein both the first logical channel and the secondlogical channel have data available for transmission; indicating, in theBSR MAC control element, a buffer status corresponding to the secondlogical channel group when the second logical channel has a highestpriority among a set of established logical channels mapping to at leastthe second serving cell and with data available for transmission,wherein the BSR MAC control element includes the buffer statuscorresponding to only the second logical channel group; and whenreceiving another uplink grant for another transmission in the firstserving cell and a condition to include a Long BSR MAC control elementin the another transmission is fulfilled and both the first logicalchannel and the second logical channel have data available fortransmission, indicating, in the Long BSR MAC control element, both abuffer status corresponding to the first logical channel group and thebuffer status corresponding to the second logical channel group.
 5. Thecommunication device of claim 4, wherein the processor is furtherconfigured to execute the program code stored in the memory to implementsmall cell enhancement by: when receiving a new another uplink grant fora new another transmission in the second serving cell and a newcondition to include the BSR MAC control element in the new anothertransmission is fulfilled and the first logical channel has dataavailable for transmission and the second logical channel does not havedata available for transmission, indicating, in the BSR MAC controlelement, the buffer status corresponding to the first logical channelgroup when the set of established logical channels is empty and thefirst logical channel has highest priority among all established logicalchannels with data available for transmission.
 6. A communication devicefor implementing small cell enhancement, comprising: a control circuit;a processor installed in the control circuit; a memory installed in thecontrol circuit and operatively coupled to the processor; wherein theprocessor is configured to execute a program code stored in the memoryto implement small cell enhancement by: connecting to multiple servingcells; triggering a Buffer Status Report (BSR) due to expiry of aperiodic buffer status reporting timer; triggering a Scheduling Request(SR) due to the triggering of the BSR; transmitting the SR on a PhysicalUplink Control Channel (PUCCH) of a second serving cell, andtransmitting a Medium Access Control (MAC) control element correspondingto the BSR in a first serving cell; wherein the first serving cell isselected based on where an uplink grant is received if the connectedserving cells are controlled by a same evolved Node B (eNB), and whereinmultiple periodic buffer status reporting timers are used to trigger theBSR and the first serving cell corresponds to the expired periodicbuffer status reporting timer if the connected serving cells arecontrolled by different eNBs, and wherein a mapping between the multipleperiodic buffer status reporting timers and the connected serving cellsis configured according to information provided by network, and each ofthe multiple periodic buffer status reporting timers corresponds to oneor a group of the connected serving cells, and wherein the MAC controlelement includes status of buffered data which can be transmitted in thefirst serving cell and does not include status of buffered data whichcannot be transmitted in the first serving cell, and wherein the secondserving cell is selected based on the trigger of the BSR, and a PUCCHresource for the SR is configured in more than one of the connectedserving cells of the communication device.
 7. The communication deviceof claim 6, wherein a mapping between MAC entities and the connectedserving cells is configured according to the information provided by thenetwork.
 8. The communication device of claim 6, wherein multiple MACentities are used by the communication device when the connected servingcells are controlled by the different eNBs and one MAC entitycorresponds to one eNB.
 9. A method of a User Equipment (UE), the methodcomprising: connecting to multiple serving cells; triggering a BufferStatus Report (BSR) due to higher priority data arrival from a specificlogical channel or Radio Bearer (RB); triggering a Scheduling Request(SR) due to the triggering of the BSR; transmitting the SR on a PhysicalUplink Control Channel (PUCCH) of a second serving cell, andtransmitting a Medium Access Control (MAC) control element correspondingto the BSR in a first serving cell; wherein the first serving cell isselected based on where an uplink grant is received if the connectedserving cells are controlled by a same evolved Node B (eNB), and whereina mapping between logical channels and the connected serving cells isconfigured according to information provided by network, each of thelogical channels corresponds to one or a group of the connected servingcells, the first serving cell corresponds to the specific logicalchannel if the connected serving cells are controlled by different eNBs,and the MAC control element corresponding to the BSR is transmitted inthe first serving cell corresponding to the specific logical channel orRB, and wherein the MAC control element includes status of buffered datawhich can be transmitted in the first serving cell and does not includestatus of buffered data which cannot be transmitted in the first servingcell, and wherein the second serving cell is selected based on thetrigger of the BSR, and a PUCCH resource for the SR is configured inmore than one of the connected serving cells of the UE.
 10. The methodof claim 9, wherein a mapping between MAC entities and the connectedserving cells is configured according to the information provided by thenetwork.
 11. The method of claim 9, wherein multiple MAC entities areused by the UE when the connected serving cells are controlled by thedifferent eNBs and one MAC entity corresponds to one eNB.
 12. Acommunication device for implementing small cell enhancement,comprising: a control circuit; a processor installed in the controlcircuit; a memory installed in the control circuit and operativelycoupled to the processor; wherein the processor is configured to executea program code stored in the memory to implement small cell enhancementby: connecting to multiple serving cells; triggering a Buffer StatusReport (BSR) due to higher priority data arrival from a specific logicalchannel or Radio Bearer (RB); triggering a Scheduling Request (SR) dueto the triggering of the BSR; transmitting the SR on a Physical UplinkControl Channel (PUCCH) of a second serving cell, and transmitting aMedium Access Control (MAC) control element corresponding to the BSR ina first serving cell; wherein the first serving cell is selected basedon where an uplink grant is received if the connected serving cells arecontrolled by a same evolved Node B (eNB), and wherein a mapping betweenlogical channels and the connected serving cells is configured accordingto information provided by network, each of the logical channelscorresponds to one or a group of the connected serving cells, the firstserving cell corresponds to the specific logical channel if theconnected serving cells are controlled by different eNBs, and the MACcontrol element corresponding to the BSR is transmitted in the firstserving cell corresponding to the specific logical channel or RB, andwherein the MAC control element includes status of buffered data whichcan be transmitted in the first serving cell and does not include statusof buffered data which cannot be transmitted in the first serving cell,and wherein the second serving cell is selected based on the trigger ofthe BSR, and a PUCCH resource for the SR is configured in more than oneof the connected serving cells of the communication device.
 13. Thecommunication device of claim 12, wherein a mapping between MAC entitiesand the connected serving cells is configured according to theinformation provided by the network.
 14. The communication device ofclaim 12, wherein multiple MAC entities are used by the communicationdevice when the connected serving cells are controlled by the differenteNBs and one MAC entity corresponds to one eNB.
 15. A method of a UserEquipment (UE), the method comprising: connecting to multiple servingcells; triggering a Buffer Status Report (BSR) due to expiry of a bufferstatus retransmission timer; triggering a Scheduling Request (SR) due tothe triggering of the BSR; transmitting the SR on a Physical UplinkControl Channel (PUCCH) of a second serving cell, and transmitting aMedium Access Control (MAC) control element corresponding to the BSR ina first serving cell; wherein the first serving cell is selected basedon where an uplink grant is received if the connected serving cells arecontrolled by a same evolved Node B (eNB), and wherein multiple bufferstatus retransmission timers are used to trigger the BSR and the firstserving cell corresponds to the expired buffer status retransmissiontimer if the connected serving cells are controlled by different eNBs,the MAC control element corresponding to the BSR is transmitted in thefirst serving cell corresponding to the buffer status retransmissiontimer, a mapping between the multiple buffer status retransmissiontimers and the connected serving cells is configured according toinformation provided by network, and each of the multiple buffer statusretransmission timers corresponds to one or a group of the connectedserving cells, and wherein the MAC control element includes status ofbuffered data which can be transmitted in the first serving cell anddoes not include status of buffered data which cannot be transmitted inthe first serving cell, and wherein the second serving cell is selectedbased on the trigger of the BSR, and a PUCCH resource for the SR isconfigured in more than one of the connected serving cells of the UE.16. The method of claim 15, wherein a mapping between MAC entities andthe connected serving cells is configured according to the informationprovided by the network.
 17. The method of claim 15, wherein multipleMAC entities are used by the UE when the connected serving cells arecontrolled by the different eNBs and one MAC entity corresponds to oneeNB.
 18. A communication device for implementing small cell enhancement,comprising: a control circuit; a processor installed in the controlcircuit; a memory installed in the control circuit and operativelycoupled to the processor; wherein the processor is configured to executea program code stored in the memory to implement small cell enhancementby: connecting to multiple serving cells; triggering a Buffer StatusReport (BSR) due to expiry of a buffer status retransmission timer;triggering a Scheduling Request (SR) due to the triggering of the BSR;transmitting the SR on a Physical Uplink Control Channel (PUCCH) of asecond serving cell, and transmitting a Medium Access Control (MAC)control element corresponding to the BSR in a first serving cell;wherein the first serving cell is selected based on where an uplinkgrant is received if the connected serving cells are controlled by asame evolved Node B (eNB), and wherein multiple buffer statusretransmission timers are used to trigger the BSR and the first servingcell corresponds to the expired buffer status retransmission timer ifthe connected serving cells are controlled by different eNBs, the MACcontrol element corresponding to the BSR is transmitted in the firstserving cell corresponding to the buffer status retransmission timer, amapping between the multiple buffer status retransmission timers and theconnected serving cells is configured according to information providedby network, and each of the multiple buffer status retransmission timerscorresponds to one or a group of the connected serving cells, andwherein the MAC control element includes status of buffered data whichcan be transmitted in the first serving cell and does not include statusof buffered data which cannot be transmitted in the first serving cell,and wherein the second serving cell is selected based on the trigger ofthe BSR, and a PUCCH resource for the SR is configured in more than oneof the connected serving cells of the communication device.
 19. Thecommunication device of claim 18, wherein a mapping between MAC entitiesand the connected serving cells is configured according to theinformation provided by the network.
 20. The communication device ofclaim 18, wherein multiple MAC entities are used by the communicationdevice when the connected serving cells are controlled by the differenteNBs and one MAC entity corresponds to one eNB.